The goals of the leadership administration and statistical analysis core (Core C) are to provide overall leadership for the program project, provide administrative support and coordination for the activities outlined in this program project and to provide statistical guidance to analyses undertaken in each of the projects. Core C coordinates the bi-weekly meetings of the leadership team for the program project, including the project leaders and core directors. This meeting also coordinates the integration of other activities into the overall Nurses' Health Study (NHS) The core also convenes the annual meeting of the External Advisory Committee, which is chaired by Dr. Leslie Bernstein and includes members with expertise covering the topics included in this Program Project. The statistical analysis group is led by Dr. Bernard Rosner, Senior Statistician for the Nurses' Health Study (NHS) since its inception in 1976. He is supported by Dr. Catherine Berkey and a Junior Statistician, to be named. These statisticians provide statistical support for all the collaborating statisticians. Programmers in Core D perform data analysis at the direction of project investigators and the collaborating statisticians. In addition, programming support is provided for the identification of cases and controls for analyses of biomarkers in Projects 1, 2, and 3. Core D is also responsible for quality control of all analyses and documentation of data in all reports arising from the Nurses' Health Study (NHS) database.